1. Field of the Invention
The invention relates to a gas filling system for filling gas from a gas station into a gas tank mounted on a vehicle.
2. Description of the Related Art
At the time of filling, a gas-fueled vehicle, on which a gas tank is mounted, such as a fuel cell vehicle, pulls into a gas station and the gas tank is filled with the fuel gas from a filling nozzle. In a gas filling system described in Japanese Patent Application Publication No. 2004-828211 (JP-A-2004-828211), the pressure and the temperature in the gas tank are detected via sensors before starting filling and the detected data are transmitted to the gas station. A central controller on the gas station side calculates the amount of filling based on the received data. After starting filling, the central controller on the gas station side receives the pressure in the gas tank from the vehicle side to monitor whether a specified pressure is reached, to which the gas tank of the vehicle should be charged. When the specified pressure is reached, filling is ended.
When the fuel gas is hydrogen gas, there is a phenomenon that the temperature increases as filling progresses. The more the filling flow rate is increased, the steeper the increase in the gas tank temperature becomes. Thus, there is a fear that the temperature in the gas tank quickly increases and reaches the design temperature (85° C., for example) and filling of a specified amount of gas cannot be completed. On the other hand, when the filling flow rate is reduced, although the rapid increase in temperature is suppressed, the filling time becomes long. In this respect, in JP-A-2004-828211, although the calculation of the filling amount is considered, consideration is given neither to the filling flow rate nor to the filling time.
In addition, there are various kinds of gas tanks, having different heat dissipation capacities, for example. It is expected in the future that gas tanks with improved heat dissipation capacities will be developed. With a gas tank having a high heat dissipation capacity, it is possible to increase the filling flow rate and reduce the filling time. In JP-A-2004-828211, however, filling is performed without taking the characteristics of the gas tank into consideration and therefore, filling is not improved with the improvement of the characteristics of the gas tank at present and in the future.